Peugeot 508 Automatic Transmission Issues

Whoa, that sounds rough! I've heard of similar issues, and undervoltage can definitely mess with sensitive electronics like the transmission control unit. Is your battery healthy? Have you checked the voltage output from the alternator? A weak battery can cause all sorts of weirdness. I would consider looking into the transmission oil as well. When was the last time the hydraulic fluid has been changed? That might be the simplest place to start.

Thanks for the quick response. I haven't checked the alternator specifically, but the battery seems fine. As for transmission oil, I haven't touched it since I bought the car. So, you're saying low hydraulic fluid could cause these symptoms? Even at this mileage?

Okay, so the battery is likely fine. I'm not a mechanic, but yeah, old or low transmission oil can cause havoc with shifting. It loses its viscosity and lubricating properties over time, leading to jerky shifts and eventually emergency mode. 87000 km is quite a bit. Given the symptoms and the age of the oil, I'd strongly suggest getting it checked by a workshop. They can properly diagnose it and replace the oil if needed, or look deeper if it's something else. Better safe than sorry with transmissions!

Took it to the shop as suggested. The transmission oil was worn out. Changed it and everything is back to normal. Repair cost me 240€ Thanks for the advice!